This invention relates generally to the field of medical appliances, and more particularly to an intravenous flow apparatus. Intravenous flow apparatuses provide a means of administering fluid nutrients and medicaments to medical patients without requiring intervention on the part of the patient and without the delayed incorporation and often destructive modification involved when substances are ingested through the alimentary system of the patient. Consequently, their use in management of trauma in the controlled administration of substances to comatose or otherwise debilitated patients, and in the treatment of a wide range of conditions has become so common as to require no lengthy introduction.
Fundamentally, the systems in use rely principally on gravity flow from a reservoir of liquid suspended above the patient, through a flexible tube terminating in a hypodermic needle inserted into a vein of the patient. Typically, flow rate has been regulated by the use of a relatively primitive roller-clamp which is manually operated by a nurse or other attendant so as to partially occlude the tube leading from the reservoir to the patient to achieve the desired flow rate.
In operating the roller-clamp to regulate flow rate, the nurse observes the rate at which drops emerge from the reservoir into a transparent drop chamber prior to passing through the tube into the patient. By timing the drop-rate, it is possible to achieve regulation of flow rate which is adequate for some purposes.
However, this method of regulation is subject to significant errors both from the difficulty of achieving a desired initial flow rate, and from inevitable long-term changes in the rate.
In particular, the achievement of a desired initial flow rate depends not only on the skill and care of the attendant, but also on the degree to which fine adjustments can be easily secured with the existing apparatus. In this regard, the shortcomings of the relatively primitive roller-clamp make precise control difficult.
Moreover, even when the desired flow rate has initially been achieved, maintenance of this flow rate over a period of an hour or more without further attention and adjustment is highly doubtful. Since the roller-clamp operates by partially occluding the tube passing through it, and since the plastic materials used in forming such tubes are subject to relaxation over a period of time, there will nearly always be some long-term drift in flow rate.
Finally, the necessity to provide frequent attention by highly skilled nurses, and to risk the health of the patient in the event of malfunction of the apparatus are incentives to provide some better and more accurate means of flow regulation.